Important sulfate deposits have been discovered in various equatorial regions of Mars : the canyons of Valles Marineris, chaotic terrains, and Meridiani plains. In order to explain the chemical composition of these deposits and the formation of such a large volume of sediments displaying the same composition and various and extensive terrains, one of the latest hypotheses suggests a glacial origin. The aim of this thesis is to evaluate the consistency of this hypothesis by an integrated morphological and mineralogical study of sulfates found on the North Polar Cap and on equatorial chaotic terrains (Aram Chaos). The analysis of the North Polar Cap reveals that all the superficial sediments contain gypsum. These sulfate-bearing particles have been released directly from the ice cap by sublimation. Winds are then responsible for the reworking of these sediments and their accumulation in the circumpolar dune field. The analysis of Aram Chaos sulfate deposits reveals some bright, layered outcrops, similar to those observed in Valles Marineris and in Meridiani Planum ; they contain a mixture of monohydrated sulfates, ferric oxides and hydrated minerals. These deposits could also originate from glacial processes because climate models and morphological analyses show that, during periods of high obliquity, ice accumulations can have formed in the lower latitudes. Moreover, the observation of terrestrial analogs in Antarctica demonstrates that sulfates can form in ice by post-depositional processes. These processes could reproduce the chemical composition of the Martian equatorial deposits if ice and some volcanic materials were accumulated at the same time.
Nature and origin of sulfate deposits in equatorial and polar regions of Mars. Morphological and mineralogical comparison of Aram Chaos and the North Polar Cap.